Speciation of Cr(III) and Cr(VI) by Means of Melamine-Urea-Formaldehyde Resin and FAAS

Abstract

A method is described for the quantitative preconcentration and separation of trace chromium in water by adsorption on melamine-urea-formaldehyde resin. Cr(VI) is enriched from aqueous solutions on the resin. After elution the Cr(VI) is determined by FAAS. The capacity of the resin is maximal at $ pH 2. Total chromium can be determined by the method after oxidation of Cr(III) to Cr(VI) by hydrogen peroxide. The relative standard deviations (10 replicate analyses) for 10 mg/L levels of Cr(VI), Cr(III) and total chromium were 1.5, 3.5 and 2.8% respectively. The procedure has been applied to the determination and speciation of chromium in lake water, tap water and chromium-plating baths.

Multiwalled carbon nanotubes for speciation of chromium in environmental samples

“…Oxidation of Cr(III) to Cr(VI) has been performed by using the procedure given in literature [35,36]. After adjustment of the pH of the solution pH 10, 10 mL of 3% hydrogen peroxide was added.…”

Speciation of Cr(III) and Cr(VI) after column solid phase extraction on Amberlite XAD-2010

“…Then Cr(III) ions in the model solutions were oxidized to Cr(VI) by using H 2 O 2 in basic media according to procedure given by Demirata [26]. Because of the quantitative recoveries for Cr(VI) were obtained at pH 2.5, the pH of the basic solution was adjusted to pH 2.5 by the addition of 0.1 mol L −1 HNO 3 carefully.…”

“…Oxidation of Cr(III) to Cr(VI) has been performed by using the procedure given in literature [26,27]. After adjustment of the pH of the solution pH 10, 10 mL of 3% hydrogen peroxide was added.…”

Indirect speciation of Cr(III) and Cr(VI) in water samples by selective separation and preconcentration on a newly synthesized chelating resin

“…Therefore, a separation/preconcentration technique is necessary, prior to the determination of chromium by an instrumental technique [6]. For this purpose, various separation and preconcentration methods, such as liquid-liquid extraction [7], coprecipitation [1,8], cloud point extraction [9][10][11], ion exchange [12], and solid phase extraction [13][14][15][16] have been widely used for the speciation of Cr(III) and Cr(VI).…”